Around 60 other containers on the P&O freighter, called the Norstream, are being searched for people.

"This is a humanitarian issue and the welfare of these patients is a priority," said Mr Roe.

The ship containers are around 40ft long and almost airtight when closed.

The container was loaded on to the ship at 10pm last night for the eight hour crossing. It is not known where it originated from.

Mr Roe said the survivors would be interviewed with the help of interpreters.

He said police will investigate "the gangs or whoever may be involved in this conspiracy to bring these people in this way over to this country."

DISCOVERY: 35 people were found in a shipping container [Eastnews]

An Essex Police spokesman said: "Thirty-one people, including adults and children of both genders, were found inside.

"One man has sadly died and the others have significant health problems.

"They are being treated by ambulance crews and are being taken to local hospitals."

Some survivors have been taken to Basildon Hospital which has been taped off by police.

Others are at South End Hospital and Royal London Hospital, Whitechapel.

Their conditions are not thought to be life threatening.

A "decontamination zone" was set up near where the stowaways were found.

A Public Health England spokesman said there was no sign of infectios disease risk.

"If it was Ebola, health care professionals are so alert at the moment to signs and symptoms that should there have been anyone who was showing symptoms we would have been notified immediately," she said.

"I think we can be confident that we are not dealing with that."

MAJOR INCIDENT: Some survivors were taken to Basildon Hospital [Eastnews]

South Basildon and East Thurrock MP Stephen Metcalfe called the discovery was "tragic".

"The fact that so many people appear to have travelled so far and are so desperate to get into the UK - either on their own or being trafficked is really very sad," he said.

The Conservative MP said the country needs "to get to the root causes of what is motivating people to go to such extreme lengths to travel from other parts of the world to get into the UK" and tackle people-trafficking.

Police are working with staff from Port of Tilbury, UK Border Force, the East of England Ambulance Service and Belgian authorities.

Belgium police say the lorry they believe delivered the container in Zeebrugge has been identified thanks to CCTV but they do not yet know where it originated.